The invention relates to ankle replacement prostheses, systems, and associated surgical procedures.
Until the early to mid 1970""s, patients with injured or diseased ankle joints commonly resulting from osteoarthritis (age-related wear of the joints), or rheumatoid arthritis (generalized joint inflammation causing destructive changes), or traumatic arthritis (damage to a joint from a direct injury), had few satisfactory options when their ankle joints failed. Non-surgical options included weight loss, activity modification, medication, injections, braces and therapeutic shoes. The available surgical techniques included ankle arthroscopy (endoscopic examination of the joint), ankle arthrotomy (cutting into the joint to expose the interior) and debridement (opening the joint and removing bone spurs), osteotomy (cutting the bone to realign the joint), ankle fusion (removing the joint and making it stiff), and total ankle arthroplasty (removing the ankle joint and replacing it with an artificial substitute).
Many of the prior art surgical procedures were riddled with problems for the patient. While early success was realized, there was a high long-term failure rate due to complications such as infection, loosening, and collapse, which lead to additional extensive surgical procedures.
Previous ankle replacement systems typically include a talar member, fixed to the talus, as one of their main functioning components. The talus, however, is relatively small, providing a small area of bone for fixation. Also, in most of these ankle replacement systems, the talar component is cemented to the talus. The combination of fixation with bone cement to a small fixation area allows for erosion of the cement from the fixation area and an increase in compliance due to formation of a soft tissue capsule over time. This contributes to aseptic loosening and migration of the device.
Previous ankle replacement systems are typically installed through incisions made at or near the ankle and make use of extramedullary alignment and guidance techniques. Such surgical procedures require making large incisions at the ankle, moving the tendons and other soft tissue aside, and separating the tibia and fibula from the talusxe2x80x94essentially detaching the foot from the legxe2x80x94to install the device. Such procedures subsequently require complicated extramedullary realignment and reattachment of the foot. These procedures commonly result in infection and extended healing time with possible replacement failure from improper extramedullary realignment. The surgery also has increased risks associated with cutting or damaging neighboring nerves and tendons which may lead to further complications.
There remains a need for a total ankle replacement system that reduces the occurrence of subsidence and aseptic loosening while retaining the majority of the foot""s natural motion.
The invention provides minimally invasive intramedullary guidance systems and methods for installing ankle prostheses. The intramedullary guidance systems and methods make possible better long term results, because the bony cuts of the talus and tibia are properly oriented, allowing proper alignment of the total ankle prosthesis.
One aspect of the invention provides systems and methods that locate a bone cutting guide in the ankle joint between a tibial bone region and a talar bone region. The systems and methods align the cutting guide in a desired orientation with the talar and tibial bone regions using an intramedullary locating element on the cutting guide that fits within an intramedullary passage formed by advancement of an intramedullary guide pin.
In one embodiment, the systems and methods enlarge the intramedullary passage by advancing a reaming device or a drill device, e.g., over the intramedullary guide pin.
In one embodiment, the systems and methods advance a cutting instrument (e.g., a saw blade) through the cutting guide to cut either the talar bone region, or the tibial bone region, or both.
In one embodiment, a guide pin is introduced through the tibia to form the intramedullary passage.
In one embodiment, the guide pin is introduced through a calcaneus bone region.
The intramedullary guidance systems and methods introduce some and/or all surgical tools and ankle prostheses components through the tibia, using minimal invasive exposure in the tibia tubercle, or retrograde through the talus, using minimal invasive exposure in planar surface of the calcaneus. The systems and methods align the operative bony cuts of the talus and tibia for the installation of one or more ankle prostheses components, and also maintain that alignment during the installation using intramedullary guidance.
The intramedullary guidance systems and methods make possible the placement of upper prosthetic devices anchored to the tibia, as well as the placement of lower prosthetic devices on the talus (which may be anchored to the calcalenous, if desired), either individually or in combination. The intramedullary guidance systems and methods create superior cuts in the tibia and/or talus to provide near-perfect alignment with the mechanical axis of the leg, without reliance upon less-perfect extramedullary guidance. The enlarged bone surfaces support the fixation of larger prosthetic bases. The intramedullary guidance systems and methods facilitate the installation of prosthesis systems that provide greater stability and stress absorption for the prosthetic ankle joint, and decrease the probability of prosthesis loosening and subsidence.
The talar prosthetic component may include with a stem that extends into the calcaneus. This allows for an increased amount of bone to help support the talar component, although reduced motion of the subtalar joint may result.
In addition, the fixation of the tibial prosthetic component may be improved when combined with intramedullary placement of a tibial stem, which attaches to the tibial plafond.
Other objects, advantages, and embodiments of the invention are set forth in part in the description which follows, and in part, will be obvious from this description, or may be learned from the practice of the invention.